Stop me if this sounds familiar: a talented young Democratic politician, a Harvard Law grad raised by a single mother, said to be the future of his party, gets the keynote address at the Democratic convention. In 2004, this story was Barack Obama‘s. Eight years later, it is Julian Castro’s.

Elected to city council at just 26, Castro, now 37, is the mayor of San Antonio and Texas Democrats’ hottest prospect. When he addresed the Democratic National Convention in Charlotte on Tuesday night, party power brokers were watching closely. It’s not just that the last relatively unknown politician to get top billing at the DNC wound up as President. It’s that Castro has the potential to become a national figure at a time when the Latino vote gets more important every election cycle, and Democrats’ bench of Latino stars is relatively shallow.

Castro’s speech was effective, if a little formulaic. He turned his family’s up-by-the-bootstraps story into a prosecution of Mitt Romney. “I think he’s a good guy,” Castro said. “He just has no idea how good he’s had it.” There was a cute moment when his three-year-old daughter flipped her hair when she realized the camera was on her, and he got the crowd going with a call and response. But ultimately, the identity of the messenger was more important than his message.

Over the last eight years, Latinos have become more than the fastest growing voting bloc in the U.S.–they’re beginning to look like the core of the Democratic party. George W. Bush made some inroads in 2004, but Obama beat John McCain among Latinos by 36 points in 2008. Since then, that lead has grown to more than 40 points, according to recent polls, despite a tighter contest overall between Obama and Mitt Romney. The Obama campaign says its lead among Latinos is transforming Western swing states like Colorado and New Mexico into Blue territory, and Democrats hope that redder states like Arizona and even Texas will eventually follow.

Despite these gains, Republicans have bested Democrats in recruiting top-talent Latino politicians to vouch for their party. 2010 saw high-profile Republican Latinos win statewide races in Nevada, New Mexico and Florida. Last week’s Republican convention in Tampa prominently featured all three of those officeholders–Governors Brian Sandoval and Susana Martinez, and Senator Marco Rubio—as well as a star turn for Texas Senate candidate Ted Cruz.

Democrats, meanwhile, have few big-name Latinos on the roster. Former New Mexico governor Bill Richardson has mostly moved on from politics after losing a presidential bid in 2008 and withdrawing from consideration for Obama’s Commerce Secretary under a cloud of corruption allegations. And while Los Angeles Mayor Antonio Villaraigosa is chairing this year’s Democratic convention and could be well-positioned to run for California Governor in 2014, alleged ethics violations and an extramarital affair with a reporter have dampened his national prospects.

That deficiency has only increased Democrats’ hope—or hype, as Republicans tell it—that Castro can take on a bigger role in the future. He has a relatively thin political resume, but as the Dallas Morning News writes, Castro looks to be a savvy operator. On Tuesday night he had the stage to prove it. As Obama knows, there are worse ways to launch a national political career.